Field of the Invention
This invention relates to an improvement of an actuator with a clutch mechanism or driving an external mechanism such as a throttle valve of a vehicle having, for example, an automatic speed control device (hereinafter merely called an "ASCD") by using a driving source such as a motor or the like.
As a conventional type of technology, there is, for example, a system disclosed in Laid-Open Japanese Patent No. 56-75935. This type of prior art relates to an ASCD, wherein it is disclosed that an electromagnetic clutch is installed between an operating system for an accelerator pedal and a servo mechanism for driving the accelerator pedal, the electromagnetic clutch having a clutch plate supported between a shaft and a leaf spring, and an excitation part positioned with clearance against the clutch plate and integrally moved with the shaft of a worm gear.
The electromagnetic clutch installed in the conventional device requires that the clutch plate be strongly attracted by an energization part in order to transmit a sufficient torque generated by a servo-motor to an operating system for an accelerator pedal, thereby necessitating an energization part of a large size. Furthermore, in the prior art, the gear part and the clutch part for transmitting torque from a servo-motor were separate and are separated at their horizontal positions; and a wide space is required for installing the gear portion and the clutch portion, resulting in a large-sized device. In the prior art, there were many component elements, and they were also expensive.